The COVID-19 pandemic has forced most of us to look at the world a little differently. One of the upsides to this is we’re putting effort into understanding the science behind how viruses spread and adjusting out actions by social distancing and using face masks accordingly.
This knowledge has uses beyond our present crisis, too. There are aspects of our everyday lives that can be improved upon with the tools used to protect ourselves from health issues arising from exposure to harmful microscopic organisms. One technology that can be useful in this area is germicidal UV light in heating, ventilation, and air conditioning (HVAC) units.
As with any technology, the internet is awash with misinformation regarding its uses and where it can be effective. We’re going to take a closer look at how germicidal ultraviolet (UV) light can impact our health, how it works, and some best practices for adopting it into our lives.
A key to preventing misinformation is gaining an understanding of the science behind the technology. Germicidal UV light is not a new tool; the first scientific paper on the subject was published in 1878. This was followed in 1903 by Niels Finsen being awarded that year’s Nobel Prize for Medicine and Physiology as a result of his work utilizing concentrated light radiation to treat Lupus Vulgaris (also known as tuberculosis of the skin).
This doesn’t mean that simple exposure to sunlight is enough to rid us of harmful microorganisms, however. According to studies, the area in which UV light that can be effective in sterilization is of a short wavelength (around 254 nanometers), known as the C-range, or UV-C. This particular light is usually weak at the earth’s surface, so stepping outside is unlikely to expose us to sufficient UV-C. However, unlike the LED lamps designed to mimic sunlight for health benefits, it would be unwise to utilize this wavelength in our home lighting, as prolonged, direct exposure is actually known to be carcinogenic to humans.
This damaging effect can be useful. The shortwave UV light disrupts the bonds that hold together the DNA, RNA, and proteins of otherwise harmful microorganisms; this effectively breaks down its structure, preventing it from multiplying. As a result, in recent years, its use has been explored in a way that is practical while preventing unnecessary exposure and harm.
So, if it’s not advisable for people to be exposed directly to UV-C wavelengths, how is it currently being used? Rather than focusing on the individual, attention is being placed on the locations that are most likely to harbor microbes that can result in illness. Gyms, schools, workplaces, restaurants and public transportation are among those areas that are considered ideal breeding grounds for germs that can cause colds, flu, and even food poisoning.
There has been a push to integrate germicidal UV light devices in areas that can help sterilize the airflow, preventing the spread of microbes without directly exposing us to the light. This can be particularly pertinent in restaurants. One eatery in Guangzhou, China, reported that a diner was infected with COVID-19 as a result of the air conditioners blowing the virus about the room. Devices being used in HVAC systems are gaining in popularity with a couple of variations on the market:
Coil Sterilization Devices. These are the most commonly utilized due to being relatively inexpensive. They come in the form of UV sticks which are installed inside the air duct and sterilize the air handler coil (the part of the air conditioner that absorbs heat and allows cool air to flow).
Air Sterilization Devices. A UV light is installed inside the HVAC return air duct, and sterilizes the moving air as it flows. This type of device is also efficient in killing airborne microbes.
There is also evidence that this technology could be used as part of a combined strategy to fight superbugs in hospitals. A 2015 study by Duke University examined how cleaning procedures in hospital treatment rooms affected the transmission of drug resistant pathogens including MRSA. Alongside replacing the standard disinfectant with bleach, germicidal UV devices were found to result in a reduction of transmission rates. This sterilization was possible in any area which there was space for light to reflect.
As with any technology, it is imperative that we take care in implementing its adoption. We need to understand the technology we’re implementing and adopt safeguards against harm. The primary risks in this area include the following:
Eyesight. Most of us are aware of the dangers involved in looking directly at UV light. Many of us have started to utilize UV-blocking glasses and contact lenses in order to prevent the cumulative damage of long periods of exposure while outside. Exposure to UV lighting can affect the lens, cornea, and retina of the eye, and precautions need to be taken by anybody with access to areas that house these devices. Inform any service personnel that UV equipment is in place, and at the very least advise them not to look directly at the light.
Skin. Prolonged, close exposure to UV-C wavelengths is known to be carcinogenic, but even short term contact can result in burns. Untrained staff should not attempt to gain access to a HVAC unit that houses UV equipment. However, if this is unavoidable, they should be provided with personal protective equipment: UV face shields, clothing that fully covers the body, and gloves.
So, can germicidal UV light help sanitize indoor air? The evidence certainly points to it being effective across a variety of environments, and its effectiveness can be enhanced when combined with other cleaning protocols. We must, however, be mindful of its limits and take precautions to prevent harm caused by exposure.